IAS reading low, Piteo Tube

[Cliff]

I had my D10 and a IAS (backup) attached to the same hoses. They read exactly the same over the entire flight envelop. GOOD  But when I installed the AOA piteo tube and put the D10 on it and left the IAS as it had been, I get a 5 to 8 MPH difference, not good   . The D10 is reading lower.  I suspect the location of the AOA tube. But is there a way to calaprate the D10 to correct for the error in the tub location  ???

Help

 

[dynonsupport]

Cliff,
The EFIS-D10 and EFIS-D10A are calibrated at the factory and are designed to read IAS correctly based on the pressure coming into them. As you saw when you had them hooked to the same source, we do read correctly. We don't have an adjustment anywhere.

Our AOA pitot works exactly the same as other pitots. In the same location, it will read the same as another pitot. Clearly in a different location, different reading are possible. How different are your two pitot locations? Are they using the same static source?

If you have a GPS, I would suggest flying a triangle or box and applying the correct formula and seeing which of your readings is correct. It is also probably a good idea to perform a leak check on the new system.

Also, may I ask why you added the Dynon Pitot instead of replacing your current one with the Dynon unit? Most customers just use the Dynon Pitot for the Dynon as well as their other ASI's.

 

[Cliff]

Thanks for your reply   .  I have been working on this problem fore a while now.

I installed the Dynown tube as close as I could to the kit location only on the other wing.
Yes, I am using only one static port.
I calabrated the IAS with the GPS when the plane first flew. (when they were on the sae port)
The Dynon piteo instalation passed the leak test OK
I used both piteos because the Kit piteo has the static port and the Dynon has the AOA.  I had plumbed the wing for the Dynon knowing it would be available later.

I am sorry to hear I can not calabrate the D10's IAS .  That would have been the easy way to fix my problem.

Question:  Will the AOA work if the D10 is getting IAS sencing from the piteo on the port wing and the AOA from the Dynon piteo on the starboard wing?

Cliff

 

[dynonsupport]

The AOA parameter is calculated in the EFIS by using the difference in pressures between the pitot pressure port (on the very tip of the AOA pitot) and the AOA pressure port (on the angled portion of the AOA pitot). If you route the kit pitot tube pressure to the EFIS and it differs slightly from the Dynon pitot pressure, this will affect the EFIS' reading slightly. It is possible that this would be calibrated out by doing the AOA calibration routine as described in the manual.

 

[Cliff]

Thanks for the reply on Eastere Sunday.  You guys really do take care of your customers.

I think I will try switching the D10 back like I had it befor and recalibrate the AOA.

Thanks again.
happy customer
Cliff

 

[dynonsupport]

Cliff,
It does seem that you should get the same reading on the opposite wing, all other things being the same. My only concen is that the static is on your other pitot. Is there any chance that your static isn't very static? Have you verified that your altitude is correct and doesn't change with airspeed? Seems unlikley, but possible.

Just grasping at straws, but the only thing IAS uses is pitot pressure over static pressure, so there are only two things that can effect that reading. You could plumb the Dynon pitot into your other IAS gauge and see if it reads low against the GPS like the EFIS is.

Also, is the Dynon pitot is the same distance from the wing and the same point along the chord as the other pitot? This can make a real difference.

Finally, using the AOA port on the Dynon and the IAS on the other pitot should work, assuming you are going straight. In a tight turn, one wing is going faster than the other, and thus the readings will be false. To be accurate in all flight attitudes, you really should keep the two ports close to one another. I think you really should try and figure out the Dynon IAS pitot problem instead of trying to sidestep it.

 

[Cliff]

OK I have my IAS problem solved. I decided to go over ever thing one more time. I found a conection that was at the wing root that was leaking. The presure test found it. The only problem was figureing out where the problem was.

I did a flight test and the two reading are not exactly the same. As they should be. I will run the AOA calabration again just to be sure things are right.
Thanks for your help!!!!!
Cliff